Indices of cardiovascular function derived from peripheral pulse wave analysis using radial applanation tonometry: a measurement repeatability study

Abstract

Pulse wave analysis (PWA) using applanation tonometry is a non-invasive technique for assessing cardiovascular function. It produces three important indices: ejection duration index (ED%), augmentation index adjusted for heart rate (AIX@75), and subendocardial viability ratio (SEVR%). The aim of this study was to assess within- and between-observer repeatability of these measurements. After resting supine for 15 minutes, 20 ambulant patients (16 male) in sinus rhythm underwent four PWA measurements on a single occasion. Two nurses (A & B) independently and alternately undertook PWA measurements using the same equipment (Omron HEM-757; SphygmoCor with Millar hand-held tonometer) blind to the other nurse's PWA measurements. Within- and between-observer differences were analysed using the Bland-Altman `limits of agreement' approach (mean difference ± 2 standard deviations, 2SD). Mean age was 56 (blood pressure, BP 136/79; pulse rate 64). BP/PWA measurements remained stable during assessment. Based on the average of two PWA measurements the mean ± 2SD between-observer difference in ED% was 0.3 ± 2.0; AIX@75 1.0 ± 3.9; and SEVR% 1.7 ± 14.2. Based on a single PWA measurement the between-observer difference was ED% 0.3 ± 3.3; AIX@75 1.7 ± 6.9; and SEVR% 0.6 ± 22.6. Within-observer differences for nurse-A were ED% 0.0 ± 5.4; AIX@75 1.5 ± 7.0; and SEVR% 1.7 ± 39.0 (nurse-B: 0.1 ± 3.8; 0.1 ± 8.0; and 0.6 ± 23.3, respectively). PWA demonstrates high levels of repeatability even when used by relatively inexperienced staff and has the potential to be included in the routine cardiovascular assessment of ambulant patients.

Keywords

applanation tonometry measurement error pulse wave analysis radial artery reproducibility

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